Research On High Precision Calibration Method Of Differential Absorption Lidar

With the continuous development of laser technology,lidar is widely used in atmospheric environment measurement.The lidar emits a laser beam.The laser beam interacts with molecules in the atmosphere.The backscattered signal is received by the telescope.The detector performs photoelectric conversion on the backscattered signal.The data acquisition card is used to collect and store the electrical signal.Finally complete the measurement of the concentration of the object to be measured However,the requirements for repeatability of detection results,comparability of data,and detection accuracy have become more stringent,which has put forward new requirements for the development of lidar.To this end,high precision calibration based on lidar is crucial.1.The calibration methods of lidar are studied comprehensively The working principles and uncertainty errors of the three methods of unit module calibration method,total system calibration method and comparative calibration are theoretically analyzed.The unit module calibration method is to split the lidar system and then calibrate each unit individually.The total system calibration method is to use a gas cell whose gas composition and concentration are adjustable.And the final result of the lidar measurement is compared with the known concentration of standard gas to calculate the deviation.The lidar comparative calibration method is to measure the gas concentration by taking the lidar and the gas cell as a whole,and then measure the gas concentration at the same time and place by using the lidar that has completed the calibration and the lidar that is to be calibrated.2.A standard gas cell is designed for the calibration of the total system calibration method.The calibration light path of differential absorption lidar and integral path differential absorption lidar is simulated by zemax.According to the actual requirements,detailed parameters such as the light source,lens and gas cell are determined.The standard gas cell was designed and processed,and the optical transmission loss experiment was carried out on the standard gas pool.The results show that the energy attenuation of laser beam is much less than 1 %.3.An IPDA lidar system for comparative calibration is developed,which is composed of light source,transceiver system,acquisition and processing system.The structure of IPDA lidar is optimized,the optical path stability is improved by using multi-mode poly-preserving ring,and the structure design of the common axis of lidar transceiver is realized.The echo laser signal is monitored by the spectral analyzer to ensure that the laser records the experimental data in the same state,so as to ensure the accuracy of the whole measurement process.The calibration of close range IPDA lidar is realized by using gas cell,and the calibration of differential absorption lidar for long distance detection is realized by using well calibrated IPDA lidar.